Agent for extinguishing and suppressing fires and explosions are in wide use. Since under some circumstances both fires and explosions can cause damage and/or injury very rapidly, often it is desirable to be able to dispense an extinguishing agent rapidly, as soon as possible after a fire or explosion is detected (or in same cases, anticipated).
However, conventional agents typically are stored at very high pressures, on the order of several hundred pounds per square inch or more. In addition, depending upon the size of the volume that is to be protected, a large amount of suppressant may be required. Thus, for at least some systems it may be desirable to combine high pressure delivery, high volume delivery, and rapid response time.
One approach that can provide these features is the use of a burst seal, also sometimes referred to as a burst disk. Typically, a pressure vessel containing suppressant will remain closed off with a burst seal during standby. When suppressant is to be dispensed, the burst seal is ruptured, allowing the suppressant to exit the pressure vessel.
Conventionally, burst seals may be ruptured using explosives. For example, a small explosive charge might be placed near the seal, so that when it is detonated the seal ruptures.
The use of explosives to rupture burst seals can result in a rapid discharge of fluid. However, the use of explosives is problematic. Explosive devices are regulated by the Department of Transportation (DOT), and thus special shipping or handling procedures may be necessary in moving them from place to place. Explosive devices are dangerous and can cause personal injury.
In addition, certain devices and/or locales may be governed by similar regulations which require special procedures, protective equipment, etc. Thus, the presence of explosives within a conventional apparatus may itself result in increased complexity, both in terms of design and maintenance and in terms of regulatory approval.
It may be known to rupture burst seals based on relative pressure differences. For example, a pressure vessel at a high pressure may have a reservoir attached thereto at a lower pressure, which in turn is disposed within an ambient pressure environment. Burst seals may be placed between the pressure vessel and the reservoir, and between the reservoir and the environment. If both of the seals have burst strengths less than the difference in pressure between the pressure vessel and the environment, the inner seal will burst, then the outer.
However, with such an arrangement the burst strength of both seals cannot be greater than what can be readily ruptured by the pressure difference between the pressure vessel and the environment. This may be of concern, especially with regard to the outer burst disk. Environments to which fluids, particularly fire suppressants, are to be delivered may include a variety of hazards that pose a risk of puncturing the outer seal. Typically, this vents the reservoir, and causes the fluid to be dispensed, possibly at an undesirable time.
In addition, the inner seal must have a minimum burst strength such that the pressure difference between the pressure vessel and the reservoir does not rupture it. Also, the outer seal must have minimum burst strength such that the pressure difference between the reservoir and the environment does not rupture it. Thus, both the seals themselves and their means of attachment may be closely constrained in terms of their required burst strength.
Moreover, systems such as that described may suffer from slow response time. In addition to any time required to vent the reservoir, the time to build up a sufficient pressure differential to rupture each of the two relatively strong seals may be greater than could be desired.
There is need for a method and apparatus for dispensing fluid that enables simplicity of construction, transportation, and use while providing rapid response time.